Controlled release fertilizers have been known for a long time. Controlled release fertilizers seek to address several issues. Generally the first issue that controlled release fertilizers seek to address is to release the fertilizer at a time when the plant most needs the fertilizer. As a result there is less fertilizer in run off water in the spring and less pollution. However in some instances it is desirable to have only one application of a fertilizer which will be released in a sustained manner over a long period of time. This approach is used for example in lawn care and in the care of golf courses.
One approach to the creation of controlled or sustained release fertilizers was to coat urea prills with a barrier coat which eroded with time. Typically the coating was sulphur although in some instances coatings of concrete have been used. This approach is fairly unsophisticated. The fertilizer such as urea leaches out of the prill through pores in the coating. Over time the coating splits and cracks open. While the approach may address the issue of fertilizer loss in the spring it does not adequately provide a sustained release over long periods of time and in a manner responsive to the biological needs of the ambient environment.
U.S. Pat. No. 3,252,786 issued May 24, 1966 and assigned to the Sun Oil Company discloses a controlled release fertilizer. The patent teaches that the fertilizer is coated with a composition comprising a waxy substance and a component selected from the group consisting of: (1) polymerized wood rosin; (2) hydrogenated wood rosin; (3) mono and polyhydric alcohol esters of polymerized, hydrogenated, and unmodified wood rosin; and (4) polyvalent metal salts of polymerized, hydrogenated and unmodified wood rosin. (Claim 1) The patent stresses the treatment of the rosin to remove the double bond in the molecule. Furthermore the patent does not stress any particular source of rosin as being better than any other source of rosin. The patent fails to suggest that rosin from the species pinus halepensis is particularly useful in the production of controlled release fertilizer.
None of the art provides a controlled release coating which interacts with the biology in the ambient environment to provide a sustained release of fertilizer in an amount required by the environment.
The rosin acids in the coating composition of the present invention provide both a high resin character to the coating and a biological control release. The resin character makes the coated product stable, nonbreakable and non crystallizing. The biological activity causes the coating to break down in the soil at a rate responsive to the demand of plants. The coatings composition contains products of natural origin possessing high biodegradability in the soil.